Data definition refers to the process of specifying the structure, format, and constraints of data within a database or information system. It involves creating a clear description of data types, relationships, and rules that govern how data can be stored, accessed, and manipulated. This ensures consistency and integrity in data management. In the context of databases, data definition is often implemented using a language called SQL (Structured Query Language). Through SQL commands, such as CREATE, ALTER, and DROP, database administrators can define tables, fields, and their attributes, establishing a framework for how data is organized and interacted with.